The present invention relates to a device at antenna systems for generating radio waves, whereby the antenna system includes a supporting structure on which there is provided at least one main radiator for transmitting radio waves and whereby high-frequency electric currents are generated in the supporting member when the main radiator is activated to transmit radio waves.
At the antenna system described above, undesired high-frequency currents occur in the supporting structure with the result, inter alia, that the radiation pattern representing the radiation of radio waves of one or more main radiators gets an undesired irregular shape and thus, the radiation gets an undesired range.
Furthermore, said undesired high-frequency currents in the supporting structure result in that the radiation from the main radiator partially starts out in the wrong direction, e.g. backwards. This means that a powerful electromagnetic field is generated behind the supporting structure, i.e. normally in those parts of the mast supporting the antenna system wherein personell resides for service or repair.